WF process and application thereof in DFN packaging

Abstract

The invention belongs to the technical field of DFN packaging, and provides a WF process and application thereof in DFN packaging, and the WF process comprises the steps: forming a groove in the side surface of a DFN packaging body, and enabling a bonding pad to extend from the bottom to the side surface; forming a nickel plating layer on the bonding pad on the side surface of the DFN packaging body by using a chemical plating method; and carrying out quality detection on the formed nickel plating layer. Through the WF technology, the welding strength and reliability of the side bonding pad of the DFN packaging body can be remarkably enhanced, and the overall performance and stability of packaging are improved; the formation of the nickel plating layer not only enhances the corrosion resistance and wear resistance of the bonding pad, but also improves the conductivity of the bonding pad, so that the DFN packaging body shows more excellent performance in application.

Description

Technical Field

[0001] The present invention relates to the technical field of DFN packaging, and in particular to a WF process and its application in DFN packaging. Background Art

[0002] DFN (Dual-Flat-no lead) packaging is a common form of electronic packaging. It is widely used in the packaging of power devices (such as MOSFET, IGBT), LED, laser diode and other electronic components due to its small size, light weight and excellent electrical performance. With the trend of high performance and miniaturization of electronic products, the demand for DFN packaging continues to increase, especially in scenarios with high power density and high reliability requirements.

[0003] The traditional DFN packaging process usually adopts reflow soldering technology, and its basic process is as follows: 1. The package (including the chip) is fixed on the substrate through a molding process. 2. Multiple pads (usually metal materials such as copper or tin) are set on the bottom of the package. 3. Flux is applied to the surface of the pads, and then the package is aligned with the corresponding pads on the PCB (printed circuit board). 4. The package and PCB are heated by reflow soldering equipment (usually using infrared heating or hot air circulation) to melt the flux and form solder, finally realizing the electrical connection between the package and the PCB.

[0004] The traditional DFN packaging process has the following major problems in practical applications: First, AOI inspection is inconvenient. Traditional AOI inspection equipment usually performs optical inspection from the top of the package, while the pad is located at the bottom of the package, resulting in the inability to directly observe the welding quality of the bottom pad, which is prone to missed inspection or false inspection. Second, the climbing performance of the solder and the wettability of the pad are insufficient. In the traditional DFN packaging process, the climbing height of the solder on the pad is insufficient, resulting in the solder being unable to evenly cover the entire pad, which is prone to forming pores or gaps, further increasing the risk of welding defects.

[0005] In summary, the traditional DFN packaging process has significant defects in welding quality and inspection efficiency. These problems not only affect the reliability of the packaged products, but also increase production costs and time. Therefore, an improved packaging process is urgently needed to solve the above problems and improve welding reliability and production efficiency by optimizing pad design, flux selection and welding process parameters.

[0006] The WF process refers to the Wettable-Flanks process. The WF process mainly optimizes the side structure design of the DFN package to improve the wettability of the pad and the welding quality, while facilitating AOI inspection.

[0007] Therefore, it is necessary to provide a WF process and its application in DFN packaging. Summary of the invention

[0008] The present invention provides a WF process and its application in DFN packaging. Through the WF process, the welding strength and reliability of the side pads of the DFN package can be significantly enhanced, and the overall performance and stability of the package are improved; the formation of the nickel plating layer not only enhances the corrosion resistance and wear resistance of the pads, but also improves the electrical conductivity of the pads, so that the DFN package shows more superior performance in application.

[0009] The present invention provides a WF process, comprising: Step 1: Create a groove on the side of the DFN package so that the pad extends from the bottom to the side; Step 2: Using a chemical electroplating method, a nickel plating layer is formed on the pads on the side of the DFN package; Step 3: Conduct quality inspection on the formed nickel plating layer.

[0010] Furthermore, the groove has an inclination angle of 30°-60° and a depth of 0.1-0.3 mm.

[0011] Furthermore, the cross section of the groove is trapezoidal or semicircular.

[0012] Furthermore, the thickness of the nickel plating layer is 6-10 μm.

[0013] Furthermore, the thickness change rate of the nickel plating layer after 108 hours of high-temperature cooking is ≤2%; the high-temperature temperature range is 120°C to 122°C.

[0014] Furthermore, the solder coverage area of ​​the nickel plating layer is ≥95%, and the porosity is ≤0.5%.

[0015] An application of a WF process in DFN packaging includes: Use WF process for packaging of DFN package; The encapsulated DFN package body is electrically connected to the external circuit by welding using the pads on the side; The performance of the packaged DFN package and external circuit is tested.

[0016] Furthermore, the thrust value of the device of the packaged DFN package is obtained based on the thrust test.

[0017] Furthermore, the pads on the side of the DFN package are optically inspected by AOI inspection equipment.

[0018] Furthermore, optical inspection of the pads on the side of the DFN package by an AOI inspection device also includes obtaining a welding quality score of the pads on the side of the DFN package, specifically: Based on a multi-angle annular light source array, the pads on the side of the DFN package are illuminated in time-sharing manner to obtain multi-angle images; Perform wavelet transform fusion on multi-angle images to generate high-contrast fused images; Use the improved U-Net++ network to segment the pad area in the high-contrast fusion image. The improved U-Net++ network integrates the CBAM attention module and the morphological constraint loss function; Based on the three-dimensional morphology reconstruction results of the pad area in the segmented high-contrast fusion image, the pad wetting angle and coverage are calculated, and the welding quality score is obtained. Based on the comparison result between the welding quality score and the set welding quality score threshold, automatic rework or production process optimization suggestions are triggered.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The present invention effectively increases the area of ​​the pad and improves the welding reliability and stability between the DFN package and the external circuit by opening a groove on the side of the DFN package and forming a nickel plating layer in the groove.

[0020] 2. The nickel plating has good corrosion resistance and high temperature resistance. After high-temperature cooking, the thickness change rate is small, which ensures the reliability of the DFN package in a long-term working environment.

[0021] 3. Optical inspection of the side pads of the DFN package through AOI equipment can quickly and accurately evaluate the welding quality, improving production efficiency and product quality.

[0022] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 A schematic diagram of the steps of a WF process method; Figure 2 A schematic diagram of the steps of a method for applying a WF process in DFN packaging; Figure 3 Schematic diagram of the method steps for obtaining a weld quality score. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0026] The present invention provides a WF process, such as Figure 1 As shown, including: Step 1: Create a groove on the side of the DFN package so that the pad extends from the bottom to the side; Step 2: Using a chemical electroplating method, a nickel plating layer is formed on the pads on the side of the DFN package; Step 3: Conduct quality inspection on the formed nickel plating layer.

[0027] The working principle of the above technical solution is as follows: in order to realize a WF process, the present invention first extends the pad from the bottom to the side of the DFN package body by opening a groove, which can increase the contact area between the pad and the external environment and provide a better adhesion basis for the subsequent electroplating process; then, a nickel plating layer is formed on the pad by a chemical electroplating method. The nickel plating layer not only has good conductivity and corrosion resistance, but also can effectively protect the pad from the influence of the external environment; finally, the formed nickel plating layer is subjected to quality inspection to ensure the uniformity and integrity of the plating layer to meet the requirements of the subsequent packaging process.

[0028] The beneficial effects of the above technical solution are as follows: by adopting the solution provided in this embodiment, the contact area of ​​the side pad of the DFN package can be effectively increased, and the reliability and stability of the connection between the pad and the outside can be improved; at the same time, the formation of the nickel plating layer not only enhances the conductivity and corrosion resistance of the pad, but also provides an additional protective layer for the package, further extending the service life of the product; in addition, through the quality inspection step, the uniformity and integrity of the plating are ensured, which effectively avoids the packaging failure caused by the plating quality problem, and improves the production efficiency and product quality.

[0029] In one embodiment, the groove has an inclination angle of 30°-60° and a depth of 0.1-0.3 mm.

[0030] The working principle of the above technical solution is: the inclination angle of the groove design is controlled between 30°-60°, which can ensure that the pad can maximize the contact area while extending to the side, while maintaining the stability and reliability of the structure, and avoid uneven plating or falling off due to excessive angles during the electroplating process; and the depth is set to 0.1-0.3mm, which is designed based on electroplating efficiency and plating quality. Too shallow may lead to insufficient adhesion of the plating, and too deep may increase the difficulty and cost of electroplating, and even affect the overall strength of the package.

[0031] The beneficial effects of the above technical solution are as follows: by adopting the solution provided in this embodiment, the groove design further strengthens the connection between the pad and the external environment, laying a solid foundation for the subsequent electroplating process; by precisely controlling the inclination angle and depth of the groove, not only the electroplating effect is optimized, but also the performance and reliability of the entire DFN package are improved.

[0032] In one embodiment, the cross section of the groove is trapezoidal or semicircular.

[0033] The working principle of the above technical solution is: the trapezoidal or semicircular cross-sectional design can further optimize the flow and distribution of the electroplating solution in the groove; the trapezoidal cross-sectional design can guide the electroplating solution to cover the pad surface more evenly through its gradually changing width, thereby reducing dead corners and unevenness during the electroplating process; and the semicircular cross-sectional design, with its smooth curve, helps the electroplating solution to form a more stable liquid film in the groove, thereby further improving the uniformity and density of the coating.

[0034] The beneficial effect of the above technical solution is: adopting the solution provided in this embodiment helps to improve the electroplating efficiency and the quality of the plating layer, thereby enhancing the overall performance and reliability of the DFN package.

[0035] In one embodiment, the thickness of the nickel plating layer is 6-10 μm.

[0036] The working principle of the above technical solution is as follows: as a key component of the DFN package, the thickness control of the nickel plating layer is crucial to the overall performance; when the thickness of the nickel plating layer is maintained in the range of 6-10μm, it can effectively enhance the bonding force between the pad and the package, while providing sufficient conductivity and corrosion resistance. The selection of this thickness is based on a comprehensive consideration of the nickel ion deposition rate, plating stress and package reliability during the electroplating process; the nickel plating layer is formed by the nickel ions in the electroplating solution undergoing a reduction reaction on the pad surface under the action of an electric field, and during the electroplating process, by precisely controlling the composition, temperature, current density and other parameters of the electroplating solution, it is possible to ensure that the nickel ions are uniformly and quickly deposited on the pad surface to form a nickel plating layer of the desired thickness. At the same time, the thickness uniformity of the nickel plating layer is also achieved by precisely controlling the electroplating time and the flow state of the electroplating solution.

[0037] The beneficial effect of the above technical solution is that the overall performance and reliability of the DFN package can be further improved by adopting the solution provided in this embodiment.

[0038] In one embodiment, the thickness change rate of the nickel plating layer after 108 hours of high-temperature cooking is ≤2%; the high-temperature temperature range is 120°C to 122°C.

[0039] The working principle of the above technical solution is: this data indicator reflects the stability of the nickel plating in high temperature and high humidity environment; the DFN package may encounter various harsh environmental conditions in actual use, especially in high temperature and high humidity environments, the stability and durability of the plating are crucial; through a 108-hour high-temperature cooking test, the temperature range of 120°C to 122°C can simulate the impact of extreme environments on nickel plating, thereby evaluating its performance in actual applications; the nickel plating thickness change rate ≤2% means that during the high-temperature cooking process, the thickness of the plating remains almost unchanged, which proves that the plating has good heat resistance and moisture resistance, and can maintain stable performance and structure in harsh environments.

[0040] The beneficial effect of the above technical solution is: adopting the solution provided in this embodiment not only helps to improve the overall reliability of the DFN package, but also prolongs its service life and meets the needs of various high-demand application scenarios.

[0041] In one embodiment, the solder coverage area of ​​the nickel plating layer is ≥95%, and the porosity is ≤0.5%.

[0042] The working principle of the above technical solution is: this data indicator reflects the good bonding ability between the nickel plating and the solder and the density of the internal plating; during the welding process of the DFN package, the solder needs to fully cover the surface of the plating to ensure good electrical connection and heat conduction. The nickel plating solder coverage area ≥95% means that most of the plating surface can be effectively covered by the solder, reducing connection problems caused by poor welding; at the same time, porosity is an important indicator to measure the internal defects of the plating. A porosity of ≤0.5% indicates that the internal structure of the plating is dense, reducing the risk of corrosion and performance degradation caused by pores.

[0043] The beneficial effect of the above technical solution is: by adopting the solution provided in this embodiment, a high solder coverage area and a low porosity are achieved, thereby improving the welding reliability and long-term stability of the DFN package.

[0044] An application of WF process in DFN packaging, such as Figure 2 As shown, including: Use WF process for packaging of DFN package; The encapsulated DFN package body is electrically connected to the external circuit by welding using the pads on the side; The performance of the packaged DFN package and external circuit is tested.

[0045] The working principle of the above technical solution is as follows: in order to realize the application of WF process in DFN packaging, the present invention applies WF process to DFN package, and this process ensures the quality and reliability of the package; then, the DFN package processed by WF process is connected to the external circuit through its side pads. This connection method not only improves the stability of the connection, but also effectively reduces the signal loss during the connection process; finally, the packaged DFN package and the external circuit are comprehensively tested for performance. This step ensures the accuracy and reliability of the entire packaging and connection process, thereby meeting the needs of high-demand application scenarios.

[0046] The beneficial effect of the above technical solution is that by adopting the solution provided in this embodiment, the application of the WF process in DFN packaging can be realized, and excellent performance and reliability are provided for the package.

[0047] In one embodiment, the thrust value of the device of the packaged DFN package is obtained based on a thrust test.

[0048] The working principle of the above technical solution is: during the thrust test, professional testing equipment is used to apply a certain thrust to the packaged DFN device to evaluate its connection strength; this test ensures that when the device is subjected to external pressure or mechanical stress, the connection between its package and the external circuit remains stable and reliable; the acquisition of thrust value not only provides important data support for device quality assessment, but also provides a reliable reference basis for subsequent application scenario selection.

[0049] The beneficial effect of the above technical solution is: by adopting the solution provided in this embodiment, the actual effect of the WF process in DFN packaging can be further verified to ensure that the packaged device can meet the application requirements of high reliability and stability.

[0050] In one embodiment, the pads on the side of the DFN package are optically inspected by AOI inspection equipment.

[0051] The working principle of the above technical solution is: during the AOI equipment inspection process, a high-resolution camera is used to capture the image of the side of the package, and the image is analyzed through an advanced image processing algorithm; this inspection can accurately identify whether there are defects in the pad, such as poor welding, missing or contamination.

[0052] The beneficial effect of the above technical solution is: adopting the solution provided by this embodiment not only improves the detection efficiency, but also ensures the quality consistency of the DFN package, providing a high-quality foundation for the subsequent electronic assembly process.

[0053] In one embodiment, optical inspection of the pads on the side of the DFN package by an AOI inspection device also includes obtaining a welding quality score of the pads on the side of the DFN package, such as Figure 3 As shown, specifically: Based on the multi-angle annular light source array, the pads on the side of the DFN package are illuminated in time-sharing mode to obtain multi-angle images; the annular LED array is used to trigger the light sources at three different angles of 0°, 30°, and 60° in time-sharing mode, and the mirror reflection is suppressed by the polarizer; Perform wavelet transform fusion on multi-angle images to retain high-frequency edge information and generate high-contrast fused images; The pad area in the high-contrast fusion image is segmented using an improved U-Net++ network, which integrates the CBAM attention module and the morphological constraint loss function. The CBAM attention module is embedded in U-Net++ to enhance the extraction of pad area features. The morphological constraint loss function is specifically: adding pad geometry constraints to the cross entropy loss. According to the reconstruction results of the three-dimensional morphology of the pad area in the segmented high-contrast fusion image, the pad wetting angle and coverage are calculated, and the welding quality score is calculated. According to the comparison result of the welding quality score and the set welding quality score threshold, automatic rework or production process optimization suggestions are triggered; specifically: Gray code stripes are projected to the side of the pad, height information is obtained through phase solution, and a three-dimensional point cloud is generated in combination with the AOI equipment image; the indicators for the welding quality score are defined; the indicators include pad wetting angle, coverage, roughness and offset distance; among them, the pad wetting angle reflects the fluidity of the solder, the coverage reflects the pad contact area ratio, and the roughness reflects the three-dimensional morphology standard deviation; the offset distance reflects the center deviation of the pad; the calculation formula for the welding quality score is: Represents the welding quality score, , Both represent global balance factors; represents the weight of wettability, represents the weight of coverage, represents the weight of wettability, represents the weight of coverage; Represents the pad wetting angle; represents coverage; Represents roughness; Represents the offset distance; Express Sigmoid normalization is performed to evaluate the wettability of the pad; Express Sigmoid normalization is performed to evaluate welding integrity; Express Sigmoid normalization is performed to evaluate the uniformity of the pad surface; Express Sigmoid normalization is performed to evaluate the alignment accuracy.

[0054] The working principle of the above technical solution is as follows: in order to accurately evaluate the welding quality of DFN package, the present invention adopts a multi-angle annular light source array to time-share irradiate the side of the pad, and comprehensively captures the detailed information of the pad by acquiring multi-angle images; the time-share trigger mechanism of the annular LED array ensures the precise control of light sources at different angles, effectively suppresses mirror reflection, and improves image quality; then the multi-angle images are fused by using wavelet transform fusion technology, which not only retains high-frequency edge information, but also generates a high-contrast fused image, providing strong support for subsequent pad area segmentation; the improved U-Net++ network plays a key role in pad area segmentation, and by embedding the CBAM attention module, it can more accurately extract pad area features and enhance the recognition ability of the model; at the same time, the introduction of the morphological constraint loss function further constrains the pad geometry and improves the segmentation accuracy; this series of optimization measures makes the segmentation of the pad area more accurate and efficient. In terms of 3D morphology reconstruction, the pad morphology is accurately reconstructed by projecting Gray code stripes onto the side of the pad, using phase solution technology to obtain height information, and combining AOI equipment images to generate 3D point clouds. On this basis, welding quality scoring indicators including pad wetting angle, coverage, roughness and offset distance are defined to comprehensively evaluate welding quality. These indicators not only reflect key information such as solder fluidity, pad contact area ratio, 3D morphology standard deviation and alignment accuracy, but also provide a strong basis for subsequent welding quality control. Finally, by comprehensively considering the weights and normalization results of various indicators, the welding quality score is calculated, and automatic rework or production process optimization suggestions are triggered based on the comparison results between the welding quality score and the set welding quality score threshold. This scoring system is not only highly accurate and reliable, but also can provide effective guidance and support for welding quality control of DFN packages.

[0055] The beneficial effects of the above technical scheme are as follows: the scheme provided in this embodiment can significantly improve the evaluation accuracy and efficiency of the welding quality of DFN packages; the multi-angle annular light source array time-sharing irradiation technology effectively solves the mirror reflection problem, improves the image quality, and lays a solid foundation for subsequent processing; the application of wavelet transform fusion technology not only retains the key details of the image, but also enhances the image contrast, making the pad area segmentation more accurate; the improved U-Net++ network combined with the CBAM attention module further improves the accuracy and efficiency of pad feature extraction, and the introduction of the morphological constraint loss function further constrains the pad geometry, ensuring high segmentation accuracy; in addition, through the three-dimensional morphology reconstruction technology and the definition of welding quality scoring indicators, a comprehensive and accurate evaluation of welding quality is achieved.

[0056] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A WF process, characterized in that: include: Step 1: Create a groove on the side of the DFN package so that the pad extends from the bottom to the side; Step 2: Using a chemical electroplating method, a nickel plating layer is formed on the pads on the side of the DFN package; Step 3: Conduct quality inspection on the formed nickel plating layer.

2. A WF process according to claim 1, characterized in that: The inclination angle of the groove is 30°-60° and the depth is 0.1-0.3mm.

3. A WF process according to claim 1, characterized in that: The cross section of the groove is trapezoidal or semicircular.

4. A WF process according to claim 1, characterized in that: The thickness of the nickel plating layer is 6-10 μm.

5. A WF process according to claim 1, characterized in that: The thickness change rate of the nickel plating layer after 108 hours of high-temperature cooking is ≤2%; the high-temperature temperature range is 120℃ to 122℃.

6. A WF process according to claim 1, characterized in that: The solder coverage area of ​​the nickel plating is ≥95% and the porosity is ≤0.5%.

7. An application of a WF process according to any one of claims 1 to 6 in DFN packaging, characterized in that: include: Use WF process for packaging of DFN package; The encapsulated DFN package body is electrically connected to the external circuit by welding using the pads on the side; The performance of the packaged DFN package and external circuit is tested.

8. The application of a WF process in DFN packaging according to claim 7, characterized in that: The thrust value of the device in the packaged DFN package is obtained based on the thrust test.

9. The application of a WF process in DFN packaging according to claim 7, characterized in that: The pads on the side of the DFN package are optically inspected by AOI inspection equipment.

10. The application of the WF process in DFN packaging according to claim 9, characterized in that: The pads on the side of the DFN package are optically inspected by AOI inspection equipment, and the soldering quality score of the pads on the side of the DFN package is obtained, specifically: Based on a multi-angle annular light source array, the pads on the side of the DFN package are illuminated in time-sharing manner to obtain multi-angle images; Perform wavelet transform fusion on multi-angle images to generate high-contrast fused images; Use the improved U-Net++ network to segment the pad area in the high-contrast fusion image. The improved U-Net++ network integrates the CBAM attention module and the morphological constraint loss function; Based on the three-dimensional morphology reconstruction results of the pad area in the segmented high-contrast fusion image, the pad wetting angle and coverage are calculated, and the welding quality score is obtained. Based on the comparison result between the welding quality score and the set welding quality score threshold, automatic rework or production process optimization suggestions are triggered.

Images